Power generation facilities operated by a gas engine using natural gas or other type of gaseous fuel as a main fuel are launched to provide a source of cleaner-burning energy. To make a gas engine perform stable and efficient operation, fuel supply valves provided for respective cylinders are controlled, and the ignition timing is also controlled. However, abnormal combustion such as knocking and misfire may nonetheless occur. It may be useful to detect and avoid abnormal combustion such as knocking and misfire at an early stage.
To avoid knocking, supply of gas fuel is halted or reduced for a cylinder in which knocking has occurred, or the ignition timing is retarded in some cases. For instance, Patent Document 1 (JP4688916B) and Patent Document 2 (JP4247842B) are known.
Patent Document 1 discloses a load leveling control in which an exhaust temperature is detected for cylinders of a gas engine, a cylinder in which knocking or misfire has appeared is detected, an amount of fuel supply to a cylinder comprising a maximum exhaust temperature is reduced, and an amount of fuel supply to a cylinder comprising a minimum exhaust temperature may be increased. Further, supply of fuel may be halted or reduced for a predetermined period of time for the cylinder in which knocking or misfire has occurred. Furthermore, the load leveling control is performed excluding the cylinder for which a measure for addressing knocking or misfire is being taken.
Patent Document 2 discloses a knocking control device for a gas engine. The magnitude of knocking is detected by a knocking sensor, and the mean value of occurrence frequency in the cylinders is compared with the occurrence frequency in a certain cylinder on the basis of a measurement value of occurrence frequency of knocking that is a predetermined value or more. If the occurrence frequency in the certain cylinder is not less than a predetermined frequency as compared to the mean value of occurrence frequency, the amount of gas injection is reduced for the certain cylinder. If the occurrence frequency in the cylinder is not more than a predetermined frequency as compared to the mean value of occurrence frequency, the amount of gas injection is increased for the cylinder. Patent Document 2 similarly discloses retarding and advancing the injection timing of the pilot fuel injection timing and the ignition timing of the spark ignition timing.